1. Field of the Invention
The present invention relates to control systems and, more particularly to systems for controlling the operation of lawn sprinklers.
2. Description of the Related Art
Numerous automatically controlled lawn sprinkler systems have heretofore been proposed. A major disadvantage of many of these is that no provision is made for turning off the sprinklers automatically during periods of natural rainfall. For example, automatic sprinkler systems are usually set to turn on in the early morning or late evening to avoid inconvenience to pedestrians and to gain the best watering effect it is exceptionally inconvenient to shut off the sprinkler when most of the people are sleeping in those hours. When early morning rain or late night rain occurs, enough water has been accumulated. Therefore, no watering from sprinklers is required. Consequently, such systems waste water and, in addition, may over water and damage the grass in lawns in which they are employed.
This problem has heretofore been recognized, and several attempts have been made to solve it.
For example, U.S. Pat. No. 3,500,844 discloses the use of two sets of spaced apart conductive members which are fixed. Rain impinging on the base closes the switch by completing a circuit between the conductive members (see col. 2, l's. 9-14 and col. 3, l's 65 to 75).
U.S. Pat. No. 4,919,165 discloses an electrical fluid level monitoring switch secured to a pair of conductors (col. 6, l's 61-64). The `165 invention uses a floating device to provide electrical contact (see col. 7, l's 16-24).
Other patents revealed in a patent search include:
U.S. Pat. Nos. 4,613,764, 3,212,714, 2,577,337, and 4,014,359.